Multilayered article comprising polypropylene impact copolymers, and method of making same

ABSTRACT

A polymer sheet includes a core layer containing a propylene impact copolymer (ICP), and a first additional layer comprising a first polymer composition. The propylene impact copolymer (ICP) in the core layer includes a matrix and a dispersed phase. The matrix comprises a polypropylene homopolymer or a propylene/alpha-olefin random copolymer which includes greater than 50 wt. % of units derived from propylene monomer. The dispersed phase includes a copolymer of ethylene and a C 3 -C 8  α-olefin. The ICP has a first melting point being greater than 100° C. (e.g., in the range of from 100° C. to 130° C.) and a second melting point. The polymer sheet can also include a second additional layer containing a second polymer composition.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/774,021, filed Sep. 9, 2015, which is a national stage entry ofInternational Application No. PCT/US2014/027590, filed Mar. 14, 2014,which claims the benefit of U.S. Provisional Application No. 61/783,894,filed Mar. 14, 2013, each of which is expressly incorporated byreference herein.

FIELD OF THE INVENTION

The disclosure relates to polymers generally. More particularly, thedisclosed subject matter relates to a polymer sheet or a fabricatedarticle having a multiple-layered structure and comprising apolypropylene impact copolymer (ICP), and the method of making thepolymer sheet or the fabricated article.

BACKGROUND OF THE INVENTION

Polypropylene compositions have gained wide commercial acceptance andusage in numerous applications because of the relatively low cost of thepolymers and the desirable properties they exhibit. In general,polypropylene polymers, particularly propylene homopolymers, have adisadvantage of being brittle with low impact resistance, especially atlow temperatures. To address these issues, manufacturers haveincorporated rubber, which forms a dispersed phase within thepolypropylene matrix. These two-phase materials are referred to asimpact copolymers or ICPs.

While impact resistance is improved, a major drawback to such materialsis the poor transparency, mostly due to the rubber particles being largeenough to affect light transmission in the heterophasic system.Accordingly, several attempts have been made to improve the transparencyof heterophasic polymer systems.

Some ICPs have been able to achieve clarity by refractive index matchingthe dispersed phase to the matrix material. Other ICPs have sought toachieve clarity by increasing dispersed phase miscibility to achieveparticles which are not large enough to affect the light transmission.While these approaches may produce clear materials, they generally lackthe stiffness and/or toughness of a conventional ICP. It would bedesirable to have an ICP which is clear, stiff and tough, and which isnot based on either technique.

SUMMARY OF THE INVENTION

The present invention provides a polymer sheet having a multiple-layeredstructure, a fabricated article having a multiple-layered structure, andmethods of making the same.

In some embodiments, the polymer sheet comprises a core layer comprisinga propylene impact copolymer (ICP), and a first additional layercomprising a first polymer composition.

The propylene ICP in the core layer comprises a matrix and a dispersedphase. The matrix comprises a polypropylene homopolymer or apropylene/alpha-olefin random copolymer which comprises greater than 50wt. % of units derived from propylene monomer. Examples of a suitablealpha-olefin as comonomer include but are not limited to butene,pentene, hexene, or octene. In some embodiments, the matrix is apropylene/alpha olefin random copolymer optionally comprising from 0.01wt. % to 5 wt. %, for example, less than about 2.0 wt. %, of ethylene.The dispersed phase comprises a copolymer of ethylene and a C₃-C₈α-olefin. The dispersed copolymer can be an ethylene-propylene copolymerin some embodiments. In some embodiments, the dispersed phase can be inthe range from 5 wt. % to 20 wt. % of the total weight of the ICP. TheICP has a first melting point being greater than 100° C. (e.g., in therange of from 100° C. to 130° C.) and a second melting point. In someembodiments, both the first melting point and the second melting pointare greater than 100° C.

In some embodiments, the first polymer composition in the firstadditional layer comprises at least one of a polypropylene homopolymer,a random copolymer of propylene comprising from 0.01 molar percent (mol.%) to 0.5 mol. % of ethylene, the propylene ICP and blends thereof.

In some embodiments, the polymer sheet further includes a secondadditional layer comprising a second polymer composition. The firstadditional layer and the second additional layer are in direct contactwith the core layer in a sandwiched structure. In some embodiments, thesecond polymer composition in the second additional layer comprises atleast one of a polypropylene homopolymer, a random copolymer ofpropylene comprising from 0.01 mol. % to 5 mol. % of ethylene, thepropylene ICP and blends thereof. In some embodiments, the firstadditional layer and the second additional layer comprise the samecomposition.

The thickness of the core layer is in the range of from 60% to 99% ofthe total thickness of the polymer sheet. The thickness of the first andthe second additional layers is in the range of from 2.5% to 40% of thetotal thickness of the polymer sheet.

In some embodiments, the first additional layer or the second additionallayer comprises a blend comprising 15-50 wt. % of the propylene ICP and50-85 wt. % of polypropylene homopolymer or a random copolymer ofpropylene comprising from 0.01 mol. % to 5 mol. % of ethylene. Forexample, in some embodiments, the first additional layer or the secondadditional layer comprises a blend comprising about 20% of the propyleneICP and about 80% of polypropylene homopolymer or a random copolymer ofpropylene comprising ethylene in the range from 0.2 mol. % to 1 mol. %.

The structure of the polymer sheet is not limited to a two-layer orthree-layer sandwiched structure. The polymer sheet can have more thanthree layers comprising any number of the core layer, the firstadditional layer and the second additional layer in any combination.

In some embodiments, the polymer sheet can have a clarity of 80% orgreater.

In some embodiments, the polymer sheet can have haze of 20% or less.

The present disclosure also provides a method of making the polymersheet as described. The method comprises a step of co-extruding the corelayer and the first additional layer. In some embodiments, the corelayer, the first additional layer and a second additional layer areco-extruded together in a single step of multi-layer coextrusion. Thefirst and the second additional layers are in direct contact with thecore layer. In some embodiments, the core layer is formed using a firstpolymer compound comprising the propylene ICP as described. The firstadditional layer and a second additional layer are formed using a secondpolymer compound. The second polymer compound comprises at least one ofa polypropylene homopolymer, a random copolymer of propylene comprisingfrom 0.01 mol. % to 5 mol. % of ethylene, the propylene ICP and blendsthereof. The thickness of the core layer can be in the range of from 60%to 99% of the total thickness of the polymer sheet. The thickness of thefirst and the second additional layers can be in the range of from 2.5%to 40% of the total thickness of the polymer sheet.

In another respect, the present disclosure provides a fabricated articleand a method for making the fabricated article, which comprises a corelayer, a first additional layer and/or a second additional layer asdescribed. The fabricated article comprises a wall, which can have astructure the same as that of the polymer sheet as described. The corelayer comprises a propylene impact copolymer (ICP), which comprises: (a)a matrix comprising a polypropylene homopolymer or apropylene/alpha-olefin random copolymer which comprises greater than 50wt. % of units derived from propylene monomer, and (b) a dispersed phasecomprising a copolymer of ethylene and a C₃-C₈ α-olefin (e.g., anethylene-propylene copolymer). The fabricated articles described hereincan have clarity values of 80% or greater and haze values of 20% orless.

Examples of a suitable alpha-olefin as comonomer include but are notlimited to butene, pentene, hexene, or octene. In some embodiments, thematrix is a propylene/alpha olefin random copolymer optionallycomprising from 0.01 wt. % to 5 wt. %, for example, less than about 2.0wt. %, of ethylene. In some embodiments, the dispersed phase can be inthe range from 5 wt. % to 20 wt. % of the total weight of the ICP. TheICP has a first melting point being greater than 100° C. (e.g., in therange of from 100° C. to 130° C.) and a second melting point. In someembodiments, both the first melting point and the second melting pointare greater than 100° C.

In some embodiments, the first or second polymer composition in thefirst or second additional layer comprises at least one of apolypropylene homopolymer, a random copolymer of propylene comprisingfrom 0.01 mol. % to 5 mol. % of ethylene, the propylene ICP and blendsthereof.

The polymer sheet and the fabricated article having selectedcompositions exhibit a combination of optical properties, such as hightransparency and low haze, together with excellent impact resistance andstiffness. The polymer sheet, which is clear and tough, is suitable forapplications such as walls for containers including but are not limitedto food containers, drinking cups, water bottles, medical devices andtoys. In some embodiments, the fabricated article is a container, forexample, a cup having low haze and high clarity.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read in conjunction with the accompanying drawings. Itis emphasized that, according to common practice, the various featuresof the drawings are not necessarily to scale. On the contrary, thedimensions of the various features are arbitrarily expanded or reducedfor clarity. Like reference numerals denote like features throughoutspecification and drawings.

FIG. 1 is a cross-sectional view of an exemplary polymer sheet inaccordance with some embodiments.

DETAILED DESCRIPTION OF THE INVENTION

This description of the exemplary embodiments is intended to be read inconnection with the accompanying drawings, which are to be consideredpart of the entire written description. In the description, relativeterms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,”“below,” “up,” “down,” “top” and “bottom” as well as derivatives thereof(e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should beconstrued to refer to the orientation as then described or as shown inthe drawing under discussion. These relative terms are for convenienceof description and do not require that the apparatus be constructed oroperated in a particular orientation. Terms concerning attachments,coupling and the like, such as “connected,” refer to a relationshipwherein structures are secured or attached to one another eitherdirectly or indirectly through intervening structures, as well as bothmovable or rigid attachments or relationships, unless expresslydescribed otherwise.

For purposes of the description hereinafter, it is to be understood thatthe embodiments described below may assume alternative variations andembodiments. It is also to be understood that the specific articles,compositions, and/or processes described herein are exemplary and shouldnot be considered as limiting.

Random copolymers, i.e., single phase polypropylene with a comonomer,have been used for applications that require clarity. These randomcopolymers, however, do not have desirable physical properties forapplications where impact copolymers are normally used, particularlyimpact resistance at cold temperatures (e.g., about 4° C.).

In order to overcome the limitation of low impact toughness, metallocenecopolymers (elastomers and plastomers) and styrenic block copolymers aresometimes blended into polypropylene. These additives work by either (a)having refractive indices that match that of polypropylene(approximately 1.50 micron) or (b) particle sizes that are small enoughnot to refract light and therefore cause haze. A blend of metallocenecopolymers and polypropylene may give a first melting peak less than100° C. (e.g., 99° C.) measured by differential scanning calorimetry(DSC) at a heating rate of 10° C./minute.

Incorporation of such additive components into polypropylene is notdesirable, for a number of reasons. For example, it requires anadditional compounding step which adds cost and complexity in bothproduction and logistics. Additionally, the metallocene elastomers andstyrenic block copolymers are often costly to produce relative toconventional Ziegler-Natta polypropylene (ZN-PP). Moreover, multiphasepropylene copolymers having good impact toughness and decreasingstiffness can be prepared by means of Ziegler-Natta catalyst systems ina multistage polymerization reaction. However, the compositions thatincorporate ethylene-propylene copolymers having a high proportion ofethylene into a polymer matrix make the multiphase propylene copolymerturbid. Poor miscibility of the dispersed phase with the polymer matrixleads to a separation of the phases and thus to turbidity and to poortransparency values of the heterogeneous copolymer. Ethylene-propylenecopolymers prepared by means of conventional Ziegler-Natta catalystsalso have a very inhomogeneous composition.

When ICPs are formed by blending a rubber with the matrix phase, it isdesirable, from a cost-to-produce standpoint, that they are preparedusing an in-reactor process, where the matrix and the dispersed phaseare formed in separate reactors, typically operated in series. Thus, itwould be desirable to have an in-reactor ICP which is clear, stiff,tough and which is not based on refractive index matching or usingrubber with increased miscibility with the matrix.

The inventors have found a new method of making propylene ICP usingZiegler-Natta catalysts in an in-reactor solution, and the resultingpropylene ICP having high clarity, low haze and high toughness. Costlyblending and the use of metallocene elastomers are not used. Thepolypropylene ICP composition resulting from Ziegler-Natta catalysts(“ZN-PP”) also includes additional components that may improveproperties relative to metallocene catalyzed elastomers.

The inventors have also determined the resulting polypropylene ICP canbe used as a core layer to form a polymer sheet (or film) or afabricated article having a multi-layered structure. The resultingpolymer sheet and the fabricated article have excellent clarity andtoughness but low haze.

The term “polymer,” as used herein, refers to a polymeric compoundprepared by polymerizing monomers, whether of the same or a differenttype. The generic term polymer thus embraces the term “homopolymer,”usually employed to refer to polymers prepared from only one type ofmonomer, as well as “copolymer” which refers to polymers prepared fromtwo or more different monomers.

“Polypropylene” shall mean polymers comprising greater than 50% byweight of units which have been derived from propylene monomer. Thisincludes polypropylene homopolymers or copolymers (meaning units derivedfrom two or more comonomers).

For brevity, unless expressly indicated otherwise, references to“polypropylene ICP” made in the present disclosure will be understood toencompass any polypropylene having good impact resistance. In someembodiments, propylene impact copolymer (ICP) has a two-phase structure,comprising: (a) a matrix comprising a polypropylene homopolymer or apropylene/alpha-olefin random copolymer which comprises greater than 50wt. % of units derived from propylene monomer, and (b) a dispersed phasecomprising a copolymer of ethylene and a C₃-C₈ α-olefin (e.g., anethylene-propylene copolymer).

Density is determined in accordance with ASTM D792.

As used herein, the “melt flow rate” (MFR) or “melt index” (units ofg/10 min or dg/min) is described according to and measured per ASTMD1238 using a load of 2.16 kg at 230° C.

As used herein, haze generally refers to an appearance cause byscattered light upon passing through a film or sheet of a material canproduce a smoky or translucent field. The haze of the present inventionis measured using ASTM D1003-97.

As used herein, clarity generally refers to the amount of luminoustransmittance described according to and measured per ASTM D1003.

As used herein, flexural modulus (expressed in units of PSI) is the onepercent secant modulus, which is further described according to andmeasured per ASTM D790 at 230° C.

As used herein, notched Izod impact strength (expressed in ft-lbs/in)was measured at 23° C. as described according to and measured per ASTMD256.

As used herein, Gardner Impact was measured at 0, 4, and 23° C.according to ASTM D5420-10 in the GC configuration. It is expressed inin-lbs.

As used herein, molar phase gas ratio (or molar gas ratio) refers to thequantity of ethylene in a dispersed phase polymerization step and, thus,the dispersed phase. It is defined by the equation:Molar Gas Ratio=mol % Ethylene/(mol % Ethylene+mol % Propylene)

In addition to ethylene and propylene, other gases such as hydrogen,propane and inert gases (e.g., nitrogen) may be used in a reactor.Nitrogen and propane, if used, are not reactive, and are used to helpwith fluidization and with increasing the heat capacity of the gasphase. Hydrogen, if used, acts as a polymer chain termination agent, andthereby controls the molecular weight of the dispersed phase. “Molar gasratio” refers to the content of ethylene in the monomers.

As used herein, differential scanning calorimetry (or “DSC”) describes athermoanalytical technique in which the difference in the amount of heatrequired to increase the temperature of a sample and reference ismeasured as a function of temperature. About 5 to 10 mg of a sheet ofthe polymer pressed at approximately 200° C. is removed with a punch dieand placed in a light aluminum pan (about 50 mg) and crimped shut. Thethermal behavior was investigated using the following profile: Thesamples were heated to 200° C. and held isothermal for 3 minutes inorder to remove any previous thermal history. The cooling and secondheating curves were recorded in the temperature range of −20° C. to 200°C. using a scan rate of 10° C./min. Melting points of crystalline phasesin a polymer composition can be determined using DSC.

As used herein, a “blender” test describes a measurement forperformance, especially impact resistance, of thin walled thermoformedarticle such as a cup during a simulated blending operation. In the“blender” test, a blender (AstroBlender Mix-N-Blender Model AM-2, serial30,370, manufactured by CRC, Inc.) was used. A sample cup (20 oz) washeld on the blender with the blender shaft therein, which was thoroughlycleaned and dried. At room temperature, the cup was filled with asuper-premium or premium ice cream to the level of about one inch belowthe rim. The ice cream was single flavored without chunks (density about0.95 g/mL), and was exposed to room temperature for less than eightminutes before filled into the cup. About 4-5 tablespoons of candychunks were then filled into the cup. The candy chucks were of firm balland/or hard crack type, and had a dimension in the range from 0.050 inchto 0.550 inch (with an average of about 0.277 inch). The candy chuckshad such a hardness that at least 40 N was required to compress asdetermined by a Tensipresser force-time curve. The candy chucks werestored at room temperature before use.

A cup collar made of stainless steel was fit onto the top of the cup.The top of the cup had a diameter equal to the diameter of the middle ofthe collar. The ice cream and the candy chucks were blended with theblender shaft half-way into the cup. The rotating blade was turned on toreach a maximum speed by gradually stepping onto a pedal of the blender.The cup was moved up and down. A failure was reported if a crackoccurred through all layer of the sidewall of the cup within 15 secondsof blending. At least six specimens were repeated for each cup, and thetimes for “pass” or “failure” were recorded.

1. Propylene Impact Copolymer (ICP)

A novel class of propylene impact copolymer (ICP) is made usingZiegler-Natta catalyst in an in-reactor solution. The propylene ICP hasa two-phase structure comprising: (a) a matrix comprising apolypropylene homopolymer or a propylene/alpha-olefin random copolymerwhich comprises greater than 50 wt. % of units derived from propylenemonomer, and (b) a dispersed phase comprising a copolymer of ethyleneand a C₃-C₈ α-olefin (e.g., an ethylene-propylene copolymer). In thematrix, examples of a suitable alpha-olefin as comonomer include but arenot limited to butene, pentene, hexene, or octene. In some embodiments,the matrix is a propylene/alpha olefin random copolymer optionallycomprising from 0.01 wt. % to 5 wt. %, for example, less than about 2.0wt. %, of ethylene. In some embodiments, the dispersed phase can be inthe range from 5 wt. % to 20 wt. % of the total weight of the ICP. TheICP has a first melting point being greater than 100° C. and a secondmelting point. In some embodiments, both the first melting point and thesecond melting point are greater than 100° C. For example, An ICP canhave a first melting point in the range of from 100° C. to 130° C.(e.g., 120° C.). The first melting point may be attributed to that ofthe dispersed phase in some embodiments. The second melting point may bein the range from 100° C. to 180° C. (e.g., 150° C., 165° C. or anyother suitable temperature). The second melting point may be attributedto that of the matrix phase in some embodiments.

The propylene ICP has high clarity, low haze and high toughness (orimpact resistance). In some embodiments, the propylene impact copolymer(ICP) provided in the present disclosure has a haze value less than 30%in a 50 mil plaque, or less than 15% in a 20 mil plaque. In someembodiments, the propylene impact copolymer can have a Gardner impactvalue greater than 200 in-lbs.

The propylene impact copolymer can be made using one or more matrixphase polymerization steps, occurring in one or more gas phase reactors;one or more dispersed phase polymerization steps, occurring in one ormore liquid phase reactors; and at least one de-gassing step. In someembodiments, the propylene ICP is made in an in-reactor comprisingmonomer including propylene and a comonomer such as ethylene. In the oneor more matrix phase polymerization steps, alpha-olefin may be used as acomonomer. Examples of a suitable alpha-olefin include but are notlimited to butene, pentene, hexene and heptene. The polymerization iscatalyzed with Ziegler-Natta catalyst. In some embodiments, thedispersed phase of the propylene ICP can have a molar gas ratio greaterthan 0.82 in-reactor. In another words, molar ratio of ethylene monomerin the dispersed phase is higher than 0.82.

Catalysts employed in the polymerization of α-olefins may becharacterized as supported catalysts or unsupported catalysts, sometimesreferred to as homogeneous catalysts. The so-called conventionalZiegler-Natta catalysts are stereospecific complexes formed from atransition metal halide and a metal alkyl or hydride, such as titaniumtetrachloride supported on an active magnesium dichloride. A supportedcatalyst component includes, but is not necessarily limited to, titaniumtetrachloride supported on an “active” anhydrous magnesium dihalide,such as magnesium dichloride or magnesium dibromide. A supportedcatalyst component may be employed in conjunction with a co-catalystsuch as an alkylaluminum compound, for example, triethylaluminum (TEAL).The Ziegler-Natta catalysts may also incorporate an electron donorcompound that may take the form of various amines, phosphenes, esters,aldehydes, and alcohols.

Single site catalyzed polyolefins can differ from Ziegler-Nattacatalyzed polyolefins in terms of molecular structure, particularlymolecular weight and co-monomer distribution. The single site catalysts,such as metallocene catalysts, can create polyolefins with a narrowmolecular weight distribution.

Metallocene catalysts are coordination compounds or cyclopentadienylgroups coordinated with transitional metals through π-bonding.Metallocene catalysts are often employed as unsupported or homogeneouscatalysts, although they also may be employed in supported catalystcomponents. With respect to the metallocene random copolymers, this termdenotes polymers obtained by copolymerizing ethylene and an α-olefin,such as propylene, butene, hexene or octene, in the presence of amonosite catalyst generally consisting of an atom of a metal which may,for example, be zirconium or titanium, and of two cyclic alkyl moleculesbonded to the metal. More specifically, the metallocene catalystsgenerally consist of two cyclopentadiene-type rings bonded to the metal.

The impact modifying components in this composition were made using aheterogeneous Ziegler-Natta catalyst. Therefore, it is expected thatseveral compositions exist in the impact modifying component. It wasunexpected that ZN-catalyzed polypropylene would produce a dispersedphase component that avoids significant haze in the final composition.In some embodiments, high ethylene content is used to achieve a producthaving both high impact resistance and low haze.

Some of the compositions of the present invention are prepared in asequential polymerization process wherein a propylene based polymer(defined as the ICP “matrix”) is prepared first, followed by thepreparation of a copolymer rubber. The composition described herein canbe prepared using a Ziegler-Natta catalyst, a co-catalyst such astriethylaluminum (“TEA”), and optionally an electron donor including thenon-limiting examples of dicyclopentyldimethoxysilane (“DPCMS”),cyclohexylmethyldimethoxysilane (“CMDMS”), diisopropyldimethoxysilane(“DIPDMS”), di-t-butyldimethoxysilane,cyclohexylisopropyldimethoxysilane, n-butylmethyldimethoxysilane,tetraethoxysilane, 3,3,3-trifluoropropylmethyldimethoxysilane, mono anddi-alkylaminotrialkoxysilanes or other electron donors known in the artor combinations thereof. Examples of different generation Ziegler-Nattacatalysts that can be applied to the practice of the present inventionare described in the “Polypropylene Handbook” by Nello Pasquini, 2ndEdition, 2005, Chapter 2 and include, but are not limited to,phthalate-based, di-ether based, succinate-based catalysts orcombinations thereof. The catalyst system is introduced at the beginningof the polymerization of propylene and is transferred with the resultingpropylene based polymer to the copolymerization reactor where it servesto catalyze the gas phase copolymerization of propylene and ethylene (ora higher alpha-olefin) to produce the rubber phase (also referred tohere as bi-polymer). The compositions can also be prepared usingmetallocene, post-metallocene, or single-site catalysts such as thosedescribed in the “Polypropylene Handbook” by Nello Pasquini, 2ndEdition, 2005.

Compositions can also be blends of elastomer with polypropylenehomopolymer and random copolymer. These compositions can be made byblending or otherwise dispersing particles of elastomer into a matrix ofthe propylene-based polymer. The propylene-based polymer and theelastomer may be combined by way of dry blending and/or melt blending.Nonlimiting examples of suitable elastomers include: olefin-basedelastomers (i.e., propylene-based elastomers and/or ethylene-basedelastomers), polyamide elastomers, elastomeric polyesters, isobutylenepolymers, polyurethane elastomers, acrylic elastomers, natural rubber,polybutadiene, polyisoprene, a styrene-based, hydrogenated blockcopolymer, and any combination of the foregoing. A styrene-based,hydrogenated block copolymer rubber has a structure containing a segmentA having a polystyrene structure at 1 to 25% by weight, A-B or A-B-Awherein, A is a segment of polystyrene structure, and B is a segment ofethylene/butene or ethylene/propylene structure. In an embodiment, theolefin-based elastomer is an ethylene-based elastomer. The term,“ethylene-based elastomer,” as used herein, is a polymer that comprisesa majority weight percent polymerized ethylene monomer (based on thetotal weight of polymerizable monomers), and optionally may comprise atleast one (or more) polymerized comonomer, the ethylene-based polymerhaving the properties of an elastomer as defined above. Nonlimitingexamples of suitable ethylene-based elastomers include ethylene/α-olefincopolymers such as ethylene and C3-C8 α olefin comonomer(ethylene/propylene copolymer, ethylene/butene copolymer,ethylene/hexene copolymer, and/or ethylene/octene copolymer), and/orolefin block copolymer (OBC). In an embodiment, the olefin-basedelastomer is an ethylene-based elastomer and has a melt index (or a meltflow rate) from about 0.5 g/10 min to about 30 g/10 min. Theethylene-based elastomer has a density from about 0.85 g/cc to about0.91 g/cc, or from about 0.86 g/cc to about 0.888 g/cc. In a furtherembodiment, the ethylene-based elastomer has a density less than 0.885g/cc or less than 0.880 g/cc.

2. Multi-Layered Polymer Sheet and Fabricated Article

FIG. 1 illustrates an exemplary polymer sheet 100 having a multi-layeredstructure in accordance with some embodiments. Polymer sheet 100 isshown for the purpose of illustration only. FIG. 1 can also illustrate awall of a fabricated article having multi-layered structure in someembodiments.

The exemplary polymer sheet 100 comprises a core layer 104 comprising apropylene impact copolymer (ICP) as described above, and a firstadditional layer 102 comprising a first polymer composition.

The propylene ICP in the core layer 104 includes a matrix and adispersed phase. The matrix comprises a polypropylene homopolymer or apropylene/alpha-olefin random copolymer which comprises greater than 50wt. % of units derived from propylene monomer. In the matrix, examplesof a suitable alpha-olefin as comonomer, if used, include but are notlimited to butene, pentene, hexene, or octene. In some embodiments, thematrix is a propylene/alpha olefin random copolymer optionallycomprising from 0.01 wt. % to 5 wt. %, for example, less than about 2.0wt. %, of ethylene. The dispersed phase comprises a copolymer ofethylene and a C₃-C₈ α-olefin (e.g., an ethylene-propylene copolymer).In some embodiments, the dispersed phase can be in the range from 5 wt.% to 20 wt. % of the total weight of the ICP.

The propylene ICP in the core layer 104 has a first melting point beinggreater than 100° C. and a second melting point. In some embodiments,both the first melting point and the second melting point are greaterthan 100° C. For example, An ICP can have a first melting point in therange of from 100° C. to 130° C. (e.g., 120° C.). The first meltingpoint may be attributed to that of the dispersed phase in someembodiments. The second melting point may be in the range from 100° C.to 180° C. (e.g., 150° C., 165° C. or any other suitable temperature).The second melting point may be attributed to that of the matrix phasein some embodiments.

In some embodiments, the first polymer composition in the firstadditional layer 102 comprises at least one of a polypropylenehomopolymer, a random copolymer of propylene comprising 0.01-5 molarpercent (mol. %) of ethylene, the propylene ICP and blends thereof.

In some embodiments, the polymer sheet 100 further comprises a secondadditional layer 106 comprising a second polymer composition. The firstadditional layer 102 and the second additional layer 106 can be indirect contact with the core layer 104 to form a sandwiched structure110 in some embodiments. The second polymer composition in the secondadditional layer 106 comprises at least one of a polypropylenehomopolymer, a random copolymer of propylene comprising 0.01-5 mol. % ofethylene, the propylene ICP and blends thereof. In some embodiments, thefirst additional layer 102 and the second additional layer 106 comprisethe same composition.

In some embodiments, the first additional layer 102 or the secondadditional layer 106 comprises a blend comprising 15-50 wt. % of thepropylene ICP and 50-85 wt. % of polypropylene homopolymer or a randomcopolymer of propylene comprising from 0.01% to 5 mol. % of ethylene. Insome embodiments, the first additional layer 102 or the secondadditional layer 106 comprises a blend comprising about 20% of thepropylene ICP and about 80% of polypropylene homopolymer or a randomcopolymer of propylene comprising ethylene in the range from 0.2 mol. %to 1 mol. %, for example, 0.5 mol. %.

The thickness of the core layer 104 can be in the range of from 60% to99%, for example, in the range of from 70% to 80%, of the totalthickness of the polymer sheet 100. The thickness of the firstadditional layer 102 and the second additional layer 104 is in the rangeof from 2.5% to 40%, for example, in the range of from 20% to 30%, ofthe total thickness of the polymer sheet 100. The first additional layer102 and the second additional layer 104 can have the same thickness. Forexample, examples of a suitable combination of layer 102/core layer104/layer 106 (with thickness in mil) include but are not limited to10/30/10, 7.5/35/7.5, and 5/40/5.

The structure of the polymer sheet 100 is not limited to a two-layer orthree-layer sandwiched structure 110. The polymer sheet 100 can havemore than three layers comprising any number of the core layer 104, thefirst additional layer 102 and the second additional layer 106 in anycombination.

The present disclosure also provides a fabricated article having a wallwith a multi-layered structure as shown in FIG. 1. For example, the wallof the fabricated article comprises a core layer 104 and a firstadditional layer 102 comprising a first polymer composition. The corelayer 104 comprises a propylene impact copolymer (ICP) having atwo-phase structure as described.

In some embodiments, the first polymer composition in the firstadditional layer 102 comprises at least one of a polypropylenehomopolymer, a random copolymer of propylene comprising from 0.01 mol. %to 5 mol. % of ethylene, the propylene ICP and blends thereof

In some embodiments, the fabricated article further comprises a secondadditional layer 106 comprising a second polymer composition. The firstadditional layer 102 and the second additional layer 106 are in directcontact with the core layer 104 to form a sandwiched structure 110 asshown in FIG. 1. In some embodiments, the first additional layer 102 andthe second additional layer 106 comprise the same composition.

The thickness of the core layer can be in the range of from 60% to 99%,for example, in the range of from 70% to 80%, of the total thickness ofthe wall. The thickness of the first additional layer 102 and the secondadditional layer 106 is in the range of from 2.5% to 40%, for example,in the range of from 20% to 30%, of the total thickness of the wall.

In some embodiments, the first additional layer or the second additionallayer comprises a blend comprising 15-50 wt. % of the propylene ICP and50-85 wt. % of polypropylene homopolymer or a random copolymer ofpropylene comprising from 0.01 mol. % to 5 mol. % of ethylene, forexample, in the range from 0.2 mol. % to 1 mol. % (e.g., 0.5 mol. %).

In some embodiments, the fabricated article is a container, for example,a cup having low haze and high clarity.

A method of making the polymer sheet (or film or laminate) 100 is alsoprovided. The method comprises a step of co-extruding the core layer 104and the first additional layer 104. In some embodiments, the core layer104, the first additional layer 102 and a second additional layer 106are co-extruded in an extruder through a single coextrusion step. Theextruder is configured so that the first additional layer 102 and thesecond additional layer 106 are in direct contact with the core layer104. In some embodiments, the core layer 104 is formed using a firstpolymer compound comprising the propylene ICP as described. The firstadditional layer 102 and a second additional layer 106 are formed usinga second polymer compound. The second polymer compound comprises atleast one of a polypropylene homopolymer, a random copolymer ofpropylene comprising from 0.01 mol. % to 5 mol. % of ethylene, thepropylene ICP and blends thereof. The thickness of the core layer 104 isin the range of from 60% to 99% (e.g., 70-80%) of the total thickness ofthe polymer sheet 100. The thickness of the first and the secondadditional layers (102 and 106) is in the range of from 2.5% to 40%(e.g., 20-30%) of the total thickness of the polymer sheet 100.

The polymer sheet can be formed by multi-layer co-extrusion. Meltedcompounds are extruded through a multi-layer multi-ply die in such apositional relation that the core layer 104 is located between the firstadditional layer 102 and the second additional layer 106. The extrudateis formed into a film, a sheet, a pipe for a container or a preform fora container. In case of a preform for a container, for example, abottle, the extruded melt resin layer laminate pipe can be subjected topreliminary blow forming into a preform having the mouth and the bottomin a mold, or the extruded melt multi-layer pipe is quenched and thencut into a predetermined length, and then both the ends of the resultingpipe having openings on both the ends are heated and formation of themouth and fusion bonding of the bottom are accomplished by compressionforming. Thus, a preform for a bottle is obtained.

The multi-layer polymer sheet or film can be preliminarily heated andthen formed into a cup by vacuum forming, air pressure forming, plugassist forming or press forming. The cup-type polypropylene containerscan be also formed by injection molding or by compressed air molding.

Formation of the laminate can also be accomplished by other techniquessuch as hot pressing, sandwich lamination, extrusion coating or thinwall injection molding

3. Examples

The following polymers were used in making examples shown in Table 1.

Polymer A is a propylene ICP made using Ziegler-Natta catalyst in anin-reactor solution. Polymer A has a two-phase structure, and is anethylene random impact copolymer (ERIC). The matrix phase is a randomcopolymer with 98 wt. % of propylene and 2 wt. % of ethylene. Thedispersed phase is 20 wt. % of the total weight of Polymer A. Thedispersed phase is made in a fluidized bed reactor that has a molar gasphase ratio of 0.90. Polymer A has two melting points of 120° C. and148° C. (measured using DSC at a rate of 10° C./min), which areattributed to the melting point of the dispersed phase and the matrixphase, respectively. Polymer A provides a flexural modulus of 150,000kpsi (ASTM D 790A, molded and tested in accordance with ASTM D 4101), amelt flow rate of 2.0 dg/min (ASTM D 1238 (230° C./2.16 kg)), a notchedIzod impact resistance of 5 ft-lb/in (ASTM D 256, molded and tested inaccordance with ASTM D 4101). Polymer A is nucleated with Milliken® NX®8000, available from Milliken Chemical Company.

Polymer B is a random copolymer of propylene comprising 0.5 wt. % ofethylene. Polymer B has a melting point of 160° C. (measured using DSC),a flexural modulus of 230,000 kpsi (ASTM D 790A, molded and tested inaccordance with ASTM D 4101), a melt flow rate of 2.0 dg/min (ASTM D1238 (230° C./2.16 kg)), a notched Izod impact resistance of 1 ft-lb/in(ASTM D 256, molded and tested in accordance with ASTM D 4101). PolymerB is nucleated with AMFINE NA-11, available from AMFINE ChemicalCorporation.

Polymer C is a random copolymer of propylene comprising 3.2 wt. % ofethylene. Polymer C has a melting point of 140° C. (measured using DSC),a flexural modulus of 170 kpsi (ASTM D 790A, molded and tested inaccordance with ASTM D 4101), a melt flow rate of 2.0 dg/min (ASTM D1238 (230° C./2.16 kg)), a notched Izod impact resistance of 1 ft-lb/in(ASTM D 256, molded and tested in accordance with ASTM D 4101).

In Table 1, the core layer 104 comprises a propylene ICP, Polymer A(i.e. the first compound). The first additional layer 102 and the secondadditional layer 106 comprise the same compound (i.e. the secondcompound). The thickness of each layer is shown in Table 1. In Examples4-9, the second compound for the first additional layer 102 and thesecond additional layer 106 is a blend comprising two or more polymers,one of which can be propylene ICP, Polymer A. The second compound forthe first additional layer 102 and the second additional layer 106, andthe first compound for the core layer 104 were co-extruded to form asandwiched structure 110 comprising the three layers 102, 104 and 106.During the coextrusion, if the second compound for layer 102 or 106comprises at least two polymers selected from Polymer A, Polymer B andPolymer C, the at least two polymers in pellet forms were fed into acorresponding hopper that connected with the extruder. The at least twopolymers were mixed in the extruder.

TABLE 1 Ext. # Layer 102 Layer 104 Layer 106 1 Polymer B Polymer APolymer B (0.003″) (0.114″) (0.003″) 2 Polymer B Polymer A Polymer B(0.006″) (0.108″) (0.006″) 3 Polymer C Polymer A Polymer C (0.00425″)(0.0765″) (0.00425″) 4 20% Polymer A/ Polymer A 20% Polymer A/ 80%Polymer C (0.0765″) 80% Polymer C (0.00425″) (0.00425″) 5 50% Polymer A/Polymer A 50% Polymer A/ 50% Polymer C (0.0765″) 50% Polymer C(0.00425″) (0.00425″) 6 20% Polymer A/ Polymer A 20% Polymer A/ 80%Polymer B (0.0765″) 80% Polymer B (0.00425″) (0.00425″) 7 25% Polymer A/Polymer A 25% Polymer A/ 75% Polymer B (0.0765″) 75% Polymer B(0.00425″) (0.00425″) 8 30% Polymer A/ Polymer A 30% Polymer A/ 70%Polymer B (0.0765″) 70% Polymer B (0.00425″) (0.00425″) 9 20% Polymer A/Polymer A 20% Polymer A/ 40% Polymer B/ (0.0765″) 40% Polymer B/ 40%Polymer C 40% Polymer C (0.00425″) (0.00425″)

The “blender” test result, and optical properties including haze andclarity of Example 1-9 are listed in Table 2.

TABLE 2 “Blender” Test Ext. # Pass Fail Haze (%) Clarity (%) 1 5 0 5.391.5 2 2 3 5 93.3 3 5 0 7.2 85.1 4 5 0 8.9 91 5 5 0 15.9 88.1 6 5 0 9.193.1 7 5 0 12.8 93.4 8 5 0 13.4 92.6 9 5 0 14.5 93.6

As shown in Table 2, the polymer sheets in the present disclosuredisplay high impact resistance, excellent clarity and low haze. Apolymer sheet (or a fabricated article) having a multi-layered structurecomprising the propylene ICP as described can be used for foodcontainers, drinking cups, water bottles, medical devices and toys. Thepropylene ICP can replace other materials such as polyolefin andpolycarbonate. For example, the polymer sheet having a multi-layeredstructure comprising the propylene ICP can be useful as a transparentcup having excellent clarity and impact toughness.

Although the subject matter has been described in terms of exemplaryembodiments, it is not limited thereto. Rather, the appended claimsshould be construed broadly, to include other variants and embodiments,which may be made by those skilled in the art.

What is claimed is:
 1. A polymer sheet, comprising: a core layercomprising a propylene impact copolymer (ICP), the propylene ICPcomprising: (a) a matrix comprising a polypropylene homopolymer or apropylene/alpha-olefin random copolymer which comprises greater than 50wt. % of units derived from propylene monomer, and (b) a dispersedcopolymer which comprises ethylene and a C₃-C₈ α-olefin, wherein the ICPhas a first melting point between 100° C. and 130° C. and a secondmelting point between 106° C. and 180° C.; and a first additional layercomprising a first polymer composition, wherein the molar ratio ofethylene monomer in the dispersed phase is greater than 0.82.
 2. Thepolymer sheet of claim 1, wherein the first polymer composition in thefirst additional layer comprises at least one of a polypropylenehomopolymer, a random copolymer of propylene comprising from 0.01 molarpercent (mol. %) to 5 mol. % of ethylene, the propylene ICP and blendsthereof.
 3. The polymer sheet of claim 1, further comprising: a secondadditional layer comprising a second polymer composition, wherein thefirst additional layer and the second additional layer are in directcontact with the core layer.
 4. The polymer sheet of claim 3, whereinthe second polymer composition in the second additional layer comprisesat least one of a polypropylene homopolymer, a random copolymer ofpropylene comprising from 0.01 molar percent (mol. %) to 5 mol. % ofethylene, the propylene ICP and blends thereof.
 5. The polymer sheet ofclaim 3, wherein the first additional layer and the second additionallayer comprise the same composition.
 6. The polymer sheet of claim 4,wherein the thickness of the core layer is in the range of from 60% to99% of the total thickness of the polymer sheet; and the thickness ofthe first and the second additional layers is in the range of from 2.5%to 40% of the total thickness of the polymer sheet.
 7. The polymer sheetof claim 3, wherein the first additional layer or the second additionallayer include a propylene ICP which comprises a blend comprising about20% of the propylene ICP and about 80% of polypropylene homopolymer or arandom copolymer of propylene comprising ethylene in the range from 0.2molar percent (mol. %) to 1 mol. %.
 8. The polymer sheet of claim 1,wherein haze is less than 20%.
 9. The polymer sheet of claim 1, whereinclarity is greater than 80%.
 10. A fabricated article, comprising: acore layer comprising a propylene impact copolymer (ICP), the propyleneICP comprising: (a) a matrix comprising a polypropylene homopolymer or apropylene/alpha-olefin random copolymer which comprises greater than 50wt. % of units derived from propylene monomer, and (b) a dispersedcopolymer which comprises ethylene and a C₃-C₈ α-olefin, wherein the ICPhas a first melting point between 100° C. and 130° C. and a secondmelting point between 106° C. and 180° C.; and a first additional layercomprising a first polymer composition, wherein the molar ratio ofethylene monomer in the dispersed phase is greater than 0.82.
 11. Thefabricated article of claim 10, wherein the first polymer composition inthe first additional layer comprises at least one of a polypropylenehomopolymer, a random copolymer of propylene comprising from 0.01 molarpercent (mol. %) to 5 mol. % of ethylene, the propylene ICP and blendsthereof.
 12. The fabricated article of claim 10, further comprising: asecond additional layer comprising a second polymer composition, whereinthe first additional layer and the second additional layer are in directcontact with the core layer.
 13. The fabricated article of claim 12,wherein the first additional layer and the second additional layercomprise the same composition.
 14. The fabricated article of claim 12,wherein the thickness of the core layer is in the range of from 60% to99% of the total thickness of the polymer sheet; and the thickness ofthe first and the second additional layers is in the range of from 2.5%to 40% of the total thickness of the polymer sheet.
 15. The fabricatedarticle of claim 10, wherein the fabricated article is a container. 16.The fabricated article of claim 10, wherein the fabricated article is acup.
 17. A method of making the polymer sheet of claim 1, comprising astep of co-extruding the core layer and the first additional layer. 18.The method of claim 17, wherein the core layer, the first additionallayer and a second additional layer are co-extruded together in a singlecoextrusion step; and the first and the second additional layers are indirect contact with the core layer.
 19. The method of claim 17, whereinthe core layer is formed using a first polymer compound comprising thepropylene ICP; and the first additional layer and a second additionallayer are formed using a second polymer compound, the second polymercompound comprising at least one of a polypropylene homopolymer, arandom copolymer of propylene comprising from 0.01 molar percent (mol.%) to 5 mol. % of ethylene, the propylene ICP and blends thereof. 20.The method of claim 17, wherein the thickness of the core layer is inthe range of from 60% to 99% of the total thickness of the polymersheet; and the thickness of a first and the second additional layer arein the range of from 1.0% to 40% of the total thickness of the polymersheet.
 21. The fabricated article of claim 10, wherein haze is less than20%.
 22. The fabricated article of claim 10, wherein clarity is greaterthan 80%.